The present invention, in some embodiments thereof, relates to a method of attaching a cell or a membrane-coated particle-of-interest to a microtube and, more particularly, but not exclusively, to electrospun microtubes which include cells or membrane-coated particles attached, entrapped or encapsulated therein which can be used in various applications such as water purification, detoxification, mineral enrichment, tissue grafts and cell-based therapy.
Water purification usually entails the removal of toxic chemicals such as mercury, mercurial compounds, and cadmium or elements such as toluene, chloroform, benzene, pesticides and herbicides. Interestingly, although these organic compounds are not found in nature and result from modern industry and motor vehicles, certain bacterial strains have evolved mechanisms for degrading them while utilizing their carbon and nitrogen atoms.
For example, Pseudomonads can be used to degrade toluene (Moat and Foster, 1995), benzene, phenol, naphthalene (Doelle, 1969) and certain hydrocarbons from oil (van der Linden et al., 1965). In addition, atrazine, a commonly used toxic herbicide that enters the water supply, can be detoxified to ammonia and carbon di-oxide via a dechlorinization reaction mediated by Pseudomonas ADP. Thus, bioparticles of Pseudomonas ADP grown on granulated active carbon were shown capable of degrading atrazine in water (Herzberg et al., 2006). However, since the granulated active carbon particles are only effective for a limited time, a carbon source (citrate) must be added to the water as it enters the purification column, which may be associated with the growth of other bacterial species and increases the costs of the purification process.
Another serious problem which occurs in some water systems is the presence of toxic heavy metals such as cadmium and mercury. Several bacterial strains such as Chromobacterium violaceum, Pseudomonas maltophila, Pseudomonas aeruginosa, Spirulina planensis, Staphylococcus aureus, Bacillus cereus, Bacillus subtilis and Escherichia coli have been found capable of removing metal contamination, destroying the toxic complex containing the metallic ions (e.g., cadmium and tellurium) or recovering valuable metals such as platinum and palladium, gold and silver from the water. For example, certain bacteria have been used to form nanoparticles of valuable metals (Brayner et al., 2007).
Nanofibers and polymeric nanofibers in particular can be produced by the electrospinning process (Reneker D H., et al., 2006; Ramakrishna S., et al., 2005; Li D, et al., 2004; PCT WO 2006/106506 to Zussman, E., et al.). Sun and co-workers (Sun Z, et al., 2003) describe the production of core-shell nanofibers (i.e., filled fibers) by co-electrospinning of two polymeric solutions using a spinneret with two co-axial capillaries. US patent application No. 20060119015 to Wehrspohn R., et al. describes the production of hollow fibers by introducing a liquid containing a polymer to a porous template material, and removal of the template following polymer solidification. PCT/IB2007/054001 to Zussman, E., et al. (which is fully incorporated herein by reference) discloses methods of producing electrospun microtubes (i.e., hollow fibers) which can be further filled with liquids and be used as microfluidics.
Salalha W., et al., 2006, describe the encapsulation of whole bacterial cells and complex bacterial viruses in electrospun single-layer fibers, in which the entrapped cells or viruses retained both physiological activity and some of their viability, even after storing the dry electrospun mats for a number of months.